1. (Field of the Invention)
The present invention relates to an apparatus for heating a green tire during vulcanizing process or the preceding process thereof.
2. (Description of the Related Art)
Conventionally, a green tire formed by a forming machine is kept in a rack of keeping place set inside a building of a vulcanizing facilities and the like under room temperature conditions, and is taken from the rack to convey to a vulcanizing machine based on a production plan. If the green tire is carried in the vulcanizing machine, for example in a bladder type vulcanizing machine, the green tire is loaded into a mold by clamping the mold, and then a heat medium under high temperature and high pressure is supplied in a bladder inserted into a tire hole, so that the bladder is extended to be close to an inner wall surface of the tire. And, by heating the inner wall surface of the tire while pressurizing it in a mold direction via the bladder, a tire groove of the mole is formed in a tread portion of the green tire. Also, by heating the green tire from the inside and the outside using the heated mold and the bladder contacting to the heat medium of high temperature, to rise temperature of the green tire up to a vulcanizing initiation temperature (at least 100˜120° C.) early, it is possible to complete a vulcanizing process in a short time.
However, as above-described prior art, if the green tire is kept for a long time under room temperature conditions, then the green tire becomes the temperature near room temperature, for example 25° C., therefore it is necessary to rise the temperature of the green tire from room temperature to initial temperature of vulcanizing when vulcanizing formation the green tire in the vulcanizing machine. In the prior art, as described above, although the vulcanizing process is completed in a short time by heating the green tire from the inside and the outside using the mold and the bladder, but the green tire has a rubber of which heat transfer ratio is low as a main component, therefore though temperature of a surface of the green tire is raised in a short time, the temperature rising of inner center particularly in a large thickness portion of the tread having large thickness and bead portion is remarkably delayed. Accordingly, vulcanizing process must be continued until temperature of the inside of the green tire is raised to complete the vulcanization, even when vulcanization of the surface side of the green tire is completed, therefore there is a problem that the vulcanizing process could not completed in a sufficiently short time.
Also, a method of irradiating a micro wave to a green tire when the green tire is kept, for preheating the green tire before vulcanizing process is adopted. But in this method, the macro wave preheats (heat) mainly the surface side of the green tire and the inside in which the temperature rising is most delayed upon vulcanization, can not be preheated sufficiently, therefore it is not a fundamental solution for completing vulcanizing process in a short time.
Furthermore, such problems are caused in a various type of a vulcanizing machine such a bladder type, a bladder-less type etc., and particularly in the bladder type vulcanizing machine, the problems become more serious since the bladder itself is formed of rubber having low heat conduction ratio.
Also, as disclosed in Japanese Patent Laid-Open No. Hei 7-96525, there is known a technique that a green tire comprising a bead and belt layer of conductive material is heated from the inside, by generating a magnetic field in the portion of the bead and belt layer to induce over-current due to electromagnetic induction thereby generating heat. However, the study has not been made for how to constitute an apparatus for efficiently heating when adopting the heating method to the vulcanization of green tire.